Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and ...Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and in addition an economic benefit to it in the construction. This study explores the possibility of replacing natural coarse aggregate with recycled concrete construction and demolition waste aggregate for general purpose concrete (i.e. plain concrete and low strength structural concrete). Different samples of CDW were extracted from different demolition sites and landfill locations around Tanta city area for the experimental investigation. CDW was crushed with all its hard constituents (e.g. concrete, brick etc.) found in the landfill. Coarse size crushed CDW was used as a coarse aggregate for concrete. Main characteristics of CDW aggregate determined in addition to the main properties of concrete which was made using this aggregate were measured. The results showed that the CDW could be transformed into recycled concrete aggregate leading to reduction in the concrete compressive strength ranged from 37% to 62% depending on the type of the CDW constituents.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression condit...In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.展开更多
Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standard...Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.展开更多
In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with ...In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with construction waste recycled aggregate to solidify silt.The mechanical properties of the solidified silt were analyzed by laboratory solidification test and microscopic examination respectively.In order to clarify the mineral composition,microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt,X-ray diffractometer(XRD),scanning electron microscope(SEM),and nitrogen adsorption pore analyzer(NA)were used to further explore and analyze the regenerated aggregate and CMPS solidified silt effectively,and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively.The experimental results show that the strength of Portland cement-mineral waste residue phosphogypsum terpolymer system curing agent increases by 107.34%than that of single Port-land cement solidified silt at 56 d,and the strength of CMPS solidified silt increases by 25.68%under the action of recycled aggregate framework.The curing age and moisture content of the silt have a high correlation with the strength of the solidified silt.Therefore,the influence law of the above two influencing factors on its mechanical properties is further explored and the strength prediction is made.The microscopic test results show that,based on the hydration of Port-land cement and the pozzolans reaction of mineral waste residue,the solidified system has produced calcium silicate hydrate gel and ettringite crystals with gelatinous properties,which helps to fill the pores and form a denser structure.展开更多
Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggreg...Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggregates(RA)and the complex interactions among multiple binder constituents.This study advances the field by developing the most extensive and rigorously preprocessed database to date,which comprises 1243 RAC mixtures containing silica fume,fly ash,and ground-granulated blast-furnace slag.A hybrid,domain-informed machine-learning framework was then proposed,coupling optimized Extreme Gradient Boosting(XGBost)with civil engineering expertise to capture the complex chemical and microstructural mechanisms that govern RAC performance.Systematic grid-search optimization(n_estimators=50,learning_rate=0.2,max_depth=7)produced superior predictive accuracy(training R^(2)=0.9923,testing R^(2)=0.937;MAE=2.378 MPa;RMSE=3.591 MPa),which outperformed Extra Trees,Light Gradient Boosting,and traditional regressors.Beyond prediction,model interpretability was achieved using Shapley additive explanations and partial dependence analyses,which revealed curing age as the dominant strength driver,while water-to-binder ratio and recycled aggregate water absorption exhibited strong negative influences.Three-dimensional interaction plots further demonstrated how optimal superplasticizer dosages reduce the strength loss associated with high recycled aggregate content.In summary,this work provides a novel,explainable,and data-driven framework that achieves high predictive accuracy with mechanistic transparency and offers a powerful,interpretable tool for the design and optimization of sustainable RAC mixtures.展开更多
To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compr...To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compressive strength of the concrete were measured.Additionally,the microstructure was analyzed using scanning electron microscopy.The evolution of pore structure parameters,including pore size distribution,pore type distribution,and nuclear magnetic resonance spectral area in the concrete,was investigated through nuclear magnetic resonance(NMR)analysis.A model correlating the concrete's pore structure with its macroscopic performance was subsequently developed based on fractal theory.The results demonstrate that an appropriate amount of PPF created a bridging effect that decelerated the progression of macro cracks,enhanced the ductility of the concrete's failure mode,and increased both cubic compressive strength and axial compressive strength,with the most effective dosage being approximately 0.6%.An appropriate amount of PPF(ranging from 0.3%to 0.6%)facilitated the formation of harmless pores and shifted the pore size distribution towards medium and small sizes.Specifically,a fiber content of 0.6%resulted in the most significant reduction in the T2 spectral area.Furthermore,the pore structure of concrete exhibits distinct fractal characteristics.As the PPF content increased,the fractal dimension initially rose and then declined,demonstrating a strong correlation with the mechanical properties.展开更多
The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental condit...The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental conditions such as load,ambient temperature,and illumination intensity,which provides theoretical support for practical engineering.The experimental results indicate that when the ambient temperature is controlled at 25℃and the illumination intensity is 30 W/m^(2),the sample prepared by soaking recycled aggregates in a 0.8%TiO_(2)/LDHs suspension exhibits the highest photocatalytic degradation rate for NO gas,reaching 72.54%.Further investigation on the influence of environmental temperature reveals that,at 25℃,the maximum photocatalytic degradation rate for NO gas is 72.9%.Moreover,at an illumination intensity of 40 W/m^(2),the maximum photocatalytic degradation rate for NO gas is 87.08%.Additionally,after three repeated photocatalytic tests,the sample demonstrates good stability,with a photocatalytic degradation rate of 58%.The nitrogen content in the eluent obtained from soaking the sample was determined to be 0.0022 mol/L,with a recovery rate of 80%.The adsorption experiment demonstrates that the sample exhibits a favorable adsorption effect on nitrate ions,reaching a maximum of 56.8%.展开更多
The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully rep...The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.展开更多
This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (...This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.展开更多
This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate ...This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate production,transportation,and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region.To obtain a detailed insight into the optimum life cycle parameters,a sensitivity study is carried out in which supplementary cementitious materials,different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered.The results show that carbon emissions were between 323 and 332 kgCO_(2)e per cubic metre of cement only natural aggregate concrete.These values can be reduced by up to 17%by replacing 25%of the cement with fly ash.By contrast,carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50%and 100%,and transportation is not included in analysis.However,the concrete with 50%recycled aggregate presented lower increase,only 0.3%and 3.4%for normal and high strength concrete,respectively.In some cases,the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%,and case-specific transportation distances were considered.In absolute values,the concrete mixes with 100%recycled aggregates and 25%fly ash had lower carbon emissions than concrete with cement and natural aggregates only.Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km)and the cement replacement by fly ash is equal or higher than 25%,considering that the mechanical properties are adequate for practical application.The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete,recommending them as an alternative to achieving global sustainability standards in construction.展开更多
The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mb：tures were prepared. The concrete mi...The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mb：tures were prepared. The concrete mixtures in series I had a water-to-binder ratio and a cement content of 0.55 and 410 kg/ m^3 , respectively. The concrete rnixtures in series II had a water-to-binder ratio and a cement content of 0.45 and 400 kg/ ml respectively. Recycled aggregate was ased as 20% , 50% , and 100% replacements of natural coarse aggregate in the concrete mixtures in both series. In cutdition, fly ash was used as 0% , 25% and 35% by weight replacements of cement. The results show that the compressive strengths of the concrete decreased as the recycled aggregate and the fly ash contents increased. The total porosity and average porosity diameter of the concrete increased us the recycled aggregate content increased. Furtherrruore , an increase in the recycled aggregate content decreased the resistance to chloride ion penetration. Nevertheless, the replacement of cement by 25% fly ush improved the resistance to chloride ion penetration and pore diameters and reduced the total porosity of the recycled aggregate concrete.展开更多
The characteristics of surface appearances,mass loss,relative dynamic modulus of elasticity and strength loss of different recycled aggregate concretes(RAC) exposed to freeze-thaw cycles were analyzed.It was found tha...The characteristics of surface appearances,mass loss,relative dynamic modulus of elasticity and strength loss of different recycled aggregate concretes(RAC) exposed to freeze-thaw cycles were analyzed.It was found that the freeze-thaw resistance of RAC could be determined by the recycled aggregate compositions and admixtures.Both the saturation degree and the air void structure were the key factors influencing the freeze-thaw damage on concrete.Some major proposed freeze-thaw deterioration mechanisms were utilized to interpret the freeze-thaw damage on recycled aggregate concrete.Meanwhile,some potential measures to enhance the freeze-thaw resistance of concrete were summarized and discussed.展开更多
Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction wa...Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.展开更多
The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this ...The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this test. The variations of relative dynamic elastic modulus Erd and water-soluble SO2-4 contents in RAC were used to evaluate degradation progress. The changes in mineral products and microstructures of interior concrete were investigated by means of X-ray diffraction(XRD), the environmental scanning electron microscope(ESEM) and X-ray computed tomography(X-CT). The results indicate that flexural loading accelerates the degradation of RAC under sulfate attack and wetting-drying cycles by expediting the transmission of SO2-4 into interior concrete. Furthermore, the accelerated effect of flexural loading is more obvious with the increase of stress ratio, that is because higher stress ratios can accelerate the extension of microcracks and generate more channels for the transmission of SO2-4. Also, more expansive products(gypsum and ettringite) are generated by the reaction of Ca(OH)2 with SO2-4, which can further accelerate the degradation of RAC.展开更多
The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FR...The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FRCA) is experimentally investigated. The basic physical performance test shows that with the increase in SC strength, FRCA exhibit lower water absorption and crushing index, meanwhile keeping higher densities. Mechanical property tests, including compressive strength, flexural strength and uniaxial compressive stress-strain tests, show that compressive strength,flexural strength and elasticity modulus of recycled sand mortars increase roughly with the increase in SC strength. The proposed mixture design method demonstrates that all of the components can be kept as the same as those in natural mortar mixture design and FRCA must be pre-wetted before making mortar mixture. Meanwhile, the reuse of higher strength SC can ensure that recycled mortar mixtures are able to achieve similar mechanical performance when compared to natural mortar designs.展开更多
The effect of recycled coarse aggregate on concrete compressive strength was investigated based on the concrete skeleton theory. For this purpose, 30 mix proportions of concrete with target cube compressive strength r...The effect of recycled coarse aggregate on concrete compressive strength was investigated based on the concrete skeleton theory. For this purpose, 30 mix proportions of concrete with target cube compressive strength ranging from 20 to 60 MPa were cast with normal coarse aggregate and recycled coarse aggregate from different strength parent concretes. Results of 28-d test show that the strength of different types of recycled aggregate affects the concrete strength obviously. The coarse aggregate added to mortar matrix plays a skeleton role and improves its compressive strength. The skeleton effect of coarse aggregate increases with the increasing strength of coarse aggregate, and normal coarse aggregate plays the highest, whereas the lowest concrete strength occurs when using the weak recycled coarse aggregate. There is a linear relationship between the concrete strength and the corresponding mortar matrix strength. Coarse aggregate skeleton formula is established, and values from experimental tests match the derived expressions.展开更多
In the past 20 years,recycled aggregate concrete(RAC),as a type of low-carbon concrete,has become a worldwide focus of research.However,the design methodology for RAC structural components remains a challenge.Conseque...In the past 20 years,recycled aggregate concrete(RAC),as a type of low-carbon concrete,has become a worldwide focus of research.However,the design methodology for RAC structural components remains a challenge.Consequently,demands for a unified design of natural aggregate concrete(NAC)and RAC components have been presented.Accordingly,this study analyses the necessity of a unified design theory and provides an in-depth demonstration of the strength determination,compressive constitutive relationship,and design method of concrete components.The coefficient of variation of RAC strength is found to be generally higher than that of NAC strength.The compressive and tensile strengths of RAC can be defined and determined using the same method as that used for NAC.The uniaxial compressive constitutive relationship between NAC and RAC has a unified mathematical expression.However,the elastic modulus of RAC decreases,and its brittleness exhibits an increasing trend compared with that of NAC.Finally,to unify the design formulae of RAC and NAC components for bearing capacity,modification factors for RAC components are proposed considering safety and reliability.Additionally,the feasibility of the proposed unified time-dependent design theory is demonstrated in terms of conceptual design and structural measures considering the effects of strength degradation and reinforcement corrosion.It is believed that this study enriches and develops the basic theory of concrete structures.展开更多
The viability of using polypropylene fibers(PPF) in concrete was largely studied. Yet, few of the existing research studies investigated the effects of PPF on the properties of concrete containing recycled concrete ag...The viability of using polypropylene fibers(PPF) in concrete was largely studied. Yet, few of the existing research studies investigated the effects of PPF on the properties of concrete containing recycled concrete aggregate(RCA). Mixes with different RCA replacement ratios and different PPF content were designed and tested. The test results showed that the addition of PPF did not change significantly the compressive strength and the density of the concrete, but slightly decreased its modulus of elasticity and Poisson’s ratio. The drop in the splitting tensile strength and the flexural strength due to RCA inclusions was to a large extent compensated by the PPF addition. The water absorption decreased and the percent voids increased with increased PPF addition. Correlations between the RCA content, the PPF content and the properties of concrete were studied. Useful regression models were proposed to predict the properties of concrete in relevant ranges of RCA and PPF content.展开更多
Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufac...Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufacturing method named ＂W3T4＂ was proposed to improve the performances of interracial transition zone （ITZ） between recycled aggregate and mortar. The mechanical properties and the durability of RAC were tested, which show that this new manufacturing method improves the properties of RAC, and the GGBS with finest size makes a great contribution to the performance of RAC due to its better filling effect and much earlier pozzolanic reaction. Combined with GGBS, the effects of PHS on the retardation of setting time can be alleviated and the synergistic effect helps to make a more compact RAC. For the RAC with 25% of the recycled aggregate （RA） replacement and 10% PHS ＋ 10% GGBS additives, the compressive strength increases by 25.4%, but the permeability decreases by 64.3% with respect to the reference concrete made with nature aggregates. The micro-mechanisms of these improvements were investigated by the scanning electron microscope （SEM）. The SEM images show that the new manufacturing method, adding superfine pozzolanic powders and super-plasticizer benefits, makes a much denser ITZ in RAC.展开更多
文摘Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and in addition an economic benefit to it in the construction. This study explores the possibility of replacing natural coarse aggregate with recycled concrete construction and demolition waste aggregate for general purpose concrete (i.e. plain concrete and low strength structural concrete). Different samples of CDW were extracted from different demolition sites and landfill locations around Tanta city area for the experimental investigation. CDW was crushed with all its hard constituents (e.g. concrete, brick etc.) found in the landfill. Coarse size crushed CDW was used as a coarse aggregate for concrete. Main characteristics of CDW aggregate determined in addition to the main properties of concrete which was made using this aggregate were measured. The results showed that the CDW could be transformed into recycled concrete aggregate leading to reduction in the concrete compressive strength ranged from 37% to 62% depending on the type of the CDW constituents.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金Funded by the Project of National Key Research and Development Program of China(No.2019YFC1906202)。
文摘In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.
文摘Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.
基金Funded by the Jiangsu Province Industry University Research Project(No.BY20231142)the Yangzhou Science&Technology Program(No.YZ2023061)the Zhenjiang Science&Technology Program(No.SH2022018)。
文摘In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with construction waste recycled aggregate to solidify silt.The mechanical properties of the solidified silt were analyzed by laboratory solidification test and microscopic examination respectively.In order to clarify the mineral composition,microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt,X-ray diffractometer(XRD),scanning electron microscope(SEM),and nitrogen adsorption pore analyzer(NA)were used to further explore and analyze the regenerated aggregate and CMPS solidified silt effectively,and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively.The experimental results show that the strength of Portland cement-mineral waste residue phosphogypsum terpolymer system curing agent increases by 107.34%than that of single Port-land cement solidified silt at 56 d,and the strength of CMPS solidified silt increases by 25.68%under the action of recycled aggregate framework.The curing age and moisture content of the silt have a high correlation with the strength of the solidified silt.Therefore,the influence law of the above two influencing factors on its mechanical properties is further explored and the strength prediction is made.The microscopic test results show that,based on the hydration of Port-land cement and the pozzolans reaction of mineral waste residue,the solidified system has produced calcium silicate hydrate gel and ettringite crystals with gelatinous properties,which helps to fill the pores and form a denser structure.
基金supported by the Ongoing Research Funding Program(Grant No.ORFT-2025-025-6)at King Saud University,Riyadh,Saudi Arabia.
文摘Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggregates(RA)and the complex interactions among multiple binder constituents.This study advances the field by developing the most extensive and rigorously preprocessed database to date,which comprises 1243 RAC mixtures containing silica fume,fly ash,and ground-granulated blast-furnace slag.A hybrid,domain-informed machine-learning framework was then proposed,coupling optimized Extreme Gradient Boosting(XGBost)with civil engineering expertise to capture the complex chemical and microstructural mechanisms that govern RAC performance.Systematic grid-search optimization(n_estimators=50,learning_rate=0.2,max_depth=7)produced superior predictive accuracy(training R^(2)=0.9923,testing R^(2)=0.937;MAE=2.378 MPa;RMSE=3.591 MPa),which outperformed Extra Trees,Light Gradient Boosting,and traditional regressors.Beyond prediction,model interpretability was achieved using Shapley additive explanations and partial dependence analyses,which revealed curing age as the dominant strength driver,while water-to-binder ratio and recycled aggregate water absorption exhibited strong negative influences.Three-dimensional interaction plots further demonstrated how optimal superplasticizer dosages reduce the strength loss associated with high recycled aggregate content.In summary,this work provides a novel,explainable,and data-driven framework that achieves high predictive accuracy with mechanistic transparency and offers a powerful,interpretable tool for the design and optimization of sustainable RAC mixtures.
基金Funded by the Natural Science Foundation of Shaanxi Province(No.2023-JC-QN-0553)。
文摘To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compressive strength of the concrete were measured.Additionally,the microstructure was analyzed using scanning electron microscopy.The evolution of pore structure parameters,including pore size distribution,pore type distribution,and nuclear magnetic resonance spectral area in the concrete,was investigated through nuclear magnetic resonance(NMR)analysis.A model correlating the concrete's pore structure with its macroscopic performance was subsequently developed based on fractal theory.The results demonstrate that an appropriate amount of PPF created a bridging effect that decelerated the progression of macro cracks,enhanced the ductility of the concrete's failure mode,and increased both cubic compressive strength and axial compressive strength,with the most effective dosage being approximately 0.6%.An appropriate amount of PPF(ranging from 0.3%to 0.6%)facilitated the formation of harmless pores and shifted the pore size distribution towards medium and small sizes.Specifically,a fiber content of 0.6%resulted in the most significant reduction in the T2 spectral area.Furthermore,the pore structure of concrete exhibits distinct fractal characteristics.As the PPF content increased,the fractal dimension initially rose and then declined,demonstrating a strong correlation with the mechanical properties.
基金Funded by the National Natural Science Foundation of China(No.52478281)the Natural Science Foundation of Zhejiang Province(No.LZ22E080003)the Science and Technology Project of Zhejiang Provincial Department of Transport(No.202225)。
文摘The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental conditions such as load,ambient temperature,and illumination intensity,which provides theoretical support for practical engineering.The experimental results indicate that when the ambient temperature is controlled at 25℃and the illumination intensity is 30 W/m^(2),the sample prepared by soaking recycled aggregates in a 0.8%TiO_(2)/LDHs suspension exhibits the highest photocatalytic degradation rate for NO gas,reaching 72.54%.Further investigation on the influence of environmental temperature reveals that,at 25℃,the maximum photocatalytic degradation rate for NO gas is 72.9%.Moreover,at an illumination intensity of 40 W/m^(2),the maximum photocatalytic degradation rate for NO gas is 87.08%.Additionally,after three repeated photocatalytic tests,the sample demonstrates good stability,with a photocatalytic degradation rate of 58%.The nitrogen content in the eluent obtained from soaking the sample was determined to be 0.0022 mol/L,with a recovery rate of 80%.The adsorption experiment demonstrates that the sample exhibits a favorable adsorption effect on nitrate ions,reaching a maximum of 56.8%.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_3174)Taizhou Science and Technology Support Programme(Social Development)Directive Project(No.TS202432)。
文摘The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.
基金Funded by the National Natural Science Foundation of China (No.52078068)the Natural Science Foundation of Jiangsu Province (No.BK20220626)。
文摘This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.
文摘This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate production,transportation,and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region.To obtain a detailed insight into the optimum life cycle parameters,a sensitivity study is carried out in which supplementary cementitious materials,different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered.The results show that carbon emissions were between 323 and 332 kgCO_(2)e per cubic metre of cement only natural aggregate concrete.These values can be reduced by up to 17%by replacing 25%of the cement with fly ash.By contrast,carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50%and 100%,and transportation is not included in analysis.However,the concrete with 50%recycled aggregate presented lower increase,only 0.3%and 3.4%for normal and high strength concrete,respectively.In some cases,the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%,and case-specific transportation distances were considered.In absolute values,the concrete mixes with 100%recycled aggregates and 25%fly ash had lower carbon emissions than concrete with cement and natural aggregates only.Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km)and the cement replacement by fly ash is equal or higher than 25%,considering that the mechanical properties are adequate for practical application.The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete,recommending them as an alternative to achieving global sustainability standards in construction.
基金Funded by the Environment and Conservation Fund, the WooWheelock Green Fund andthe Hong Kong Polytechnic University
文摘The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mb：tures were prepared. The concrete mixtures in series I had a water-to-binder ratio and a cement content of 0.55 and 410 kg/ m^3 , respectively. The concrete rnixtures in series II had a water-to-binder ratio and a cement content of 0.45 and 400 kg/ ml respectively. Recycled aggregate was ased as 20% , 50% , and 100% replacements of natural coarse aggregate in the concrete mixtures in both series. In cutdition, fly ash was used as 0% , 25% and 35% by weight replacements of cement. The results show that the compressive strengths of the concrete decreased as the recycled aggregate and the fly ash contents increased. The total porosity and average porosity diameter of the concrete increased us the recycled aggregate content increased. Furtherrruore , an increase in the recycled aggregate content decreased the resistance to chloride ion penetration. Nevertheless, the replacement of cement by 25% fly ush improved the resistance to chloride ion penetration and pore diameters and reduced the total porosity of the recycled aggregate concrete.
基金Funded by the National Key Research and Development Program of China during the“13th Five-Year Plan”(No.2018 YFD1101001)。
文摘The characteristics of surface appearances,mass loss,relative dynamic modulus of elasticity and strength loss of different recycled aggregate concretes(RAC) exposed to freeze-thaw cycles were analyzed.It was found that the freeze-thaw resistance of RAC could be determined by the recycled aggregate compositions and admixtures.Both the saturation degree and the air void structure were the key factors influencing the freeze-thaw damage on concrete.Some major proposed freeze-thaw deterioration mechanisms were utilized to interpret the freeze-thaw damage on recycled aggregate concrete.Meanwhile,some potential measures to enhance the freeze-thaw resistance of concrete were summarized and discussed.
基金The National Science and Technology Support Program of China(No.2014BAC07B03)the Science and Technology Project of Transportation Committee of Beijing Government(No.2016-LZJKJ-01-006)the National Natural Science Foundation of China(No.51278016)
文摘Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.
基金The National Natural Science Foundation of China(No.51578141)the Major State Basic Research Development Program of China(No.2015CB655102)China-Japanese Research Cooperative Program-Ministry of Science and Technology in China(No.2016YFE0118200)
文摘The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this test. The variations of relative dynamic elastic modulus Erd and water-soluble SO2-4 contents in RAC were used to evaluate degradation progress. The changes in mineral products and microstructures of interior concrete were investigated by means of X-ray diffraction(XRD), the environmental scanning electron microscope(ESEM) and X-ray computed tomography(X-CT). The results indicate that flexural loading accelerates the degradation of RAC under sulfate attack and wetting-drying cycles by expediting the transmission of SO2-4 into interior concrete. Furthermore, the accelerated effect of flexural loading is more obvious with the increase of stress ratio, that is because higher stress ratios can accelerate the extension of microcracks and generate more channels for the transmission of SO2-4. Also, more expansive products(gypsum and ettringite) are generated by the reaction of Ca(OH)2 with SO2-4, which can further accelerate the degradation of RAC.
基金The National Key Research and Development Programm of China(No.2018YFD1100402-05)the National Natural Science Foundation of China(No.6505000184)
文摘The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FRCA) is experimentally investigated. The basic physical performance test shows that with the increase in SC strength, FRCA exhibit lower water absorption and crushing index, meanwhile keeping higher densities. Mechanical property tests, including compressive strength, flexural strength and uniaxial compressive stress-strain tests, show that compressive strength,flexural strength and elasticity modulus of recycled sand mortars increase roughly with the increase in SC strength. The proposed mixture design method demonstrates that all of the components can be kept as the same as those in natural mortar mixture design and FRCA must be pre-wetted before making mortar mixture. Meanwhile, the reuse of higher strength SC can ensure that recycled mortar mixtures are able to achieve similar mechanical performance when compared to natural mortar designs.
基金Supported by the National Mega-Project of Key Technology R&D Program in the 11th Five-Year Plan of China (No.2006BAJ04A04)the Education Department of Liaoning Province, China (No. 2008282)
文摘The effect of recycled coarse aggregate on concrete compressive strength was investigated based on the concrete skeleton theory. For this purpose, 30 mix proportions of concrete with target cube compressive strength ranging from 20 to 60 MPa were cast with normal coarse aggregate and recycled coarse aggregate from different strength parent concretes. Results of 28-d test show that the strength of different types of recycled aggregate affects the concrete strength obviously. The coarse aggregate added to mortar matrix plays a skeleton role and improves its compressive strength. The skeleton effect of coarse aggregate increases with the increasing strength of coarse aggregate, and normal coarse aggregate plays the highest, whereas the lowest concrete strength occurs when using the weak recycled coarse aggregate. There is a linear relationship between the concrete strength and the corresponding mortar matrix strength. Coarse aggregate skeleton formula is established, and values from experimental tests match the derived expressions.
基金the financial support from the Distinguished Young Scholars of China by the National Natural Science Foundation of China(51325802)the National Natural Science Foundation of China(51178340,52078358,and 52008304)。
文摘In the past 20 years,recycled aggregate concrete(RAC),as a type of low-carbon concrete,has become a worldwide focus of research.However,the design methodology for RAC structural components remains a challenge.Consequently,demands for a unified design of natural aggregate concrete(NAC)and RAC components have been presented.Accordingly,this study analyses the necessity of a unified design theory and provides an in-depth demonstration of the strength determination,compressive constitutive relationship,and design method of concrete components.The coefficient of variation of RAC strength is found to be generally higher than that of NAC strength.The compressive and tensile strengths of RAC can be defined and determined using the same method as that used for NAC.The uniaxial compressive constitutive relationship between NAC and RAC has a unified mathematical expression.However,the elastic modulus of RAC decreases,and its brittleness exhibits an increasing trend compared with that of NAC.Finally,to unify the design formulae of RAC and NAC components for bearing capacity,modification factors for RAC components are proposed considering safety and reliability.Additionally,the feasibility of the proposed unified time-dependent design theory is demonstrated in terms of conceptual design and structural measures considering the effects of strength degradation and reinforcement corrosion.It is believed that this study enriches and develops the basic theory of concrete structures.
基金funded by the National Council for Scientific Research in Lebanon (CNRS - Lebanon)
文摘The viability of using polypropylene fibers(PPF) in concrete was largely studied. Yet, few of the existing research studies investigated the effects of PPF on the properties of concrete containing recycled concrete aggregate(RCA). Mixes with different RCA replacement ratios and different PPF content were designed and tested. The test results showed that the addition of PPF did not change significantly the compressive strength and the density of the concrete, but slightly decreased its modulus of elasticity and Poisson’s ratio. The drop in the splitting tensile strength and the flexural strength due to RCA inclusions was to a large extent compensated by the PPF addition. The water absorption decreased and the percent voids increased with increased PPF addition. Correlations between the RCA content, the PPF content and the properties of concrete were studied. Useful regression models were proposed to predict the properties of concrete in relevant ranges of RCA and PPF content.
基金Project(51178417)supported by the National Natural Science Foundation of ChinaProject(2012R10025)supported by the Qianjiang Talent Plan of Zhejiang Province,China+2 种基金Project(2012HY006B)supported by the Marine Cross-Guide Research Funds of Zhejiang University,ChinaProject(2013FZA4015)supported by the Fundamental Research Funds for the Central Universities,ChinaProject supported by the Department of Construction of Zhejiang Province,China
文摘Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufacturing method named ＂W3T4＂ was proposed to improve the performances of interracial transition zone （ITZ） between recycled aggregate and mortar. The mechanical properties and the durability of RAC were tested, which show that this new manufacturing method improves the properties of RAC, and the GGBS with finest size makes a great contribution to the performance of RAC due to its better filling effect and much earlier pozzolanic reaction. Combined with GGBS, the effects of PHS on the retardation of setting time can be alleviated and the synergistic effect helps to make a more compact RAC. For the RAC with 25% of the recycled aggregate （RA） replacement and 10% PHS ＋ 10% GGBS additives, the compressive strength increases by 25.4%, but the permeability decreases by 64.3% with respect to the reference concrete made with nature aggregates. The micro-mechanisms of these improvements were investigated by the scanning electron microscope （SEM）. The SEM images show that the new manufacturing method, adding superfine pozzolanic powders and super-plasticizer benefits, makes a much denser ITZ in RAC.
